CDPR gains nothing by losing the Fallout titles really. Sure they cut off a bit of Bethesda funding but the games will be buyable on Steam, which I bet is the more popular platform. Bethesda is a huge company who I expect is financially very stable. I'm not a huge fan of their stuff but there's no denying FO 3, TES, and Dishonored sold/sell well so kicking them off of GOG will do little to nothing to hurt them. It's better for CDPR to get some money for selling them than no money for not, even if Bethesda makes some from it.

If the Fallout games are sold on GOG, CDPR makes some money on every copy sold. If they can only be bought on Steam, Valve makes some money. It's true that in both cases Bethesda makes money but, Valve isn't a direct competitor.

Considering how popular Steam is, I doubt Bethesda is really worried about losing out on some revenue at GOG, at least not compared to cutting off any funding to CDPR.

I would be interested to see the sales numbers, and at what price, of those games from both platforms though, just to get an idea of how much Bethesda might lose compared to how much CDPR could make.